Process and apparatus for C2 recovery

ABSTRACT

An improved process for separating a hydrocarbon bearing feed gas containing methane and lighter, C 2  (ethylene and/or ethane), and heavier components into a fraction containing predominantly methane and lighter components and a fraction containing predominantly C 2  and heavier hydrocarbon components including the steps of cooling and partially condensing and delivering the feed stream to a separator to provide a first residue vapor and a first liquid containing C 2 , directing a first part of the first liquid containing C 2  into a heavy-ends fractionation column wherein the liquid is separated into a second hydrocarbon bearing vapor residue and a second liquid product containing C 2 ; further cooling the second part of the first liquid containing C 2  and partially condensing the second hydrocarbon bearing vapor residue; combining the cooled second part of the first liquid and partially condensed second hydrocarbon-bearing vapor residue and directing them to a second separator effecting a third residue and a third liquid; cooling and directing a first part of the third liquid into the lights-ends fractionation column, to thereby condense C 2 &#39;s and heavier components while the methane is evaporated in the light-ends fractionation column to thereby obtain fourth residue vapor and liquid, heating and supplying the fourth liquid recovered from the light-ends fractionation column to the heavy-ends fractionation column as a feed thereto; conducting the second part of the third liquid to the heavy-ends fractionation column as a feed thereto.

This application is a divisional of U.S. patent application Ser. No.09/931,218, filed Aug. 16, 2001 (now U.S. Pat. No. 7,544,272), which isa divisional of U.S. patent application Ser. No. 09/527,175, filed Mar.17, 2000 (now U.S. Pat. No. 6,278,035).

BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention relates to an improved process for separating ahydrocarbon-bearing feed gas which contains methane and lightercomponents, (not necessarily all hydrocarbon components), C₂ (ethyleneand ethane), and heavier hydrocarbon components into two fractions. Thefirst fraction contains predominantly methane and lighter components andthe second fraction contains the recovered desirable C₂ and heaviercomponents. More particularly, this invention relates to a process andapparatus wherein the yield of C₂ ^(□)s is increased or alternativelyenergy consumption is reduced for a given C₂ recovery.

2. The Prior Art

Hydrocarbon-bearing gas may contain lighter components (e.g., hydrogen,nitrogen, etc.) methane, ethane, and/or ethylene, and a substantialquantity of hydrocarbons of higher molecular weight, for example,propane, butane, pentane and often their unsaturated analogs. Recentchanges in ethylene/ethane demand have created increased markets forethylene/ethane and have created a need for more efficient processeswhich yield higher recovery levels of this product. In more recenttimes, the use of cryogenic processes utilizing the principle of gasexpansion through a mechanical device to produce power whilesimultaneously extracting heat from the system have been employed. Theuse of such equipment depends upon the pressure of the gas source, thecomposition of the gas and the desired end results. In the typicalcryogenic expansion-type recovery processes used in the prior art, a gasstream under pressure is cooled by heat exchange with other streams ofthe process and/or external sources of cooling are employed such asrefrigeration systems. As the gas is cooled, liquids are condensed andare collected and separated so as to thereby obtain desiredhydrocarbons. The high pressure liquid feed is typically transferred toa demethanizer column after the pressure is adjusted to the operatingpressure of the demethanizer. In column after the pressure is adjustedto the operating pressure of the demethanizer. In such fractionatingcolumn the liquid feed is fractionated to separate the residual methaneand lighter components from the desired products of ethylene/ethane andheavier hydrocarbon components. In the ideal operation of suchseparation processes, the vapors leaving the process containsubstantially all of the methane and lighter components found in thefeed gas and substantially no ethylene/ethane or heavier hydrocarboncomponents remain. The bottom fraction leaving the demethanizertypically contains substantially all of the ethylene/ethane and heavierhydrocarbon components with very little methane or lighter componentswhich is discharged in the fluid gas outlet from the demethanizer.

A patentability search was conducted on the present invention and thefollowing references were uncovered.

Inventor U.S. Pat. No. Issue Date Harandi 4,664,784 May 12, 1987 Buck etal 4,895,584 Jan. 23, 1990 Campbell et al 5,771,712 Sep. 01, 1998Wilkinson et al 5,699,507 Jun. 30, 1998

U.S. Pat. No. 4,664,784—Issued May 12, 1987

M. N. Harandi to Mobil Oil Corporation

In a reference directed to fractionation of hydrocarbon mixtures,teachings are found on column 4, line 32 et sequitur re: a zone (81)wherein a descending liquid heavy-ends portion contacts an ascendingvaporous light-ends portion so as “ . . . to aid In heat transferbetween vapor and liquid.” (column 4, line 44).

U.S. Pat. No. 4,895,584—Issued Jan. 23, 1990

L. L. Buck et al to Pro-Quip Corporation

A reference that claims an improved process for hydrocarbon separationand teaches supplying of the liquids recovered from the light-endsfractionating column to the heavy ends fractionating column anddirecting part of the (C₂ containing) liquid from a first step intointimate contact with a second residue, which liquid provides additionalliquefied methane which acts with the partially condensed second residueas a direct contact refrigerant to thereby condense C₂ and heaviercomprising hydrocarbons while methane itself is evaporated in thelight-ends fractionation column.

On column 1, lines 56-67 the following teachings are found: “ . . . feedgas is first cooled and partially condensed and delivered to a separatorto provide a first residue vapor and a liquid containing C₂ . . . . Partof the liquid containing C₂ from the separator may be directed into aheavy-ends fractionation column wherein the liquid is separated into asecond residue containing lighter hydrocarbons and C₂ containingproducts. A part of the first residue vapors with at least part of thepartially condensed second residue are counter currently contacted andcomingled in a light-ends fractionation column (emphasis added) . . . ”

On column 2, lines 1-10 the following teachings are found: “The liquidsrecovered from the light-ends fractionation column are then fed to theheavy-ends fractionation column as a liquid feed. A portion of theliquids containing C₂ from the separator is fed into intimate contactwith the second residue prior to discharging the comingled liquids andgases into the light-ends fractionation column to thereby achieve massand heat transfer (emphasis added) to thereby liquefy a higher percentof the C₂ and heavier hydrocarbon components while the methane isvaporized” (column 2, lines 1-10).

The following Elcor Corporation references describe the recovery of C₃and heavier hydrocarbons via processes wherein counter-current contactof a stream drawn from a deethanizer with a stream in aseparator/absorber takes place:

U.S. Pat. No. 5,799,507—Issued Sep. 1, 1998

J. D. Wilkinson et al to Elcor Corporation

See column 4, line 2 re: “ . . . liquid portion of expanded streamcommingles with liquids falling downward from the absorbing section . .. ” l.o.w., the stream (36) from the deethanizer (17) flows through heatexchanger (20) to become Stream (36a) which flows into the upper sectionof separator (15) where it “ . . . contacts the vapors rising upwardthrough the absorption section” (column 5, lines 3-4).

U.S. Pat. No. 5,771,712—Issued Jun. 30, 1998

R. E. Campbell et al to Elcor Corporation

This reference teaches essentially the same as Wilkinson et al.

None of the foregoing patents discussed above embody the presentinvention.

SUMMARY OF THE INVENTION

The present invention provides processes for increasing the ethylene andethane component of the discharge from the process unit at reducedenergy consumption than the prior art. The foregoing advantage isachieved in the present invention by a process in which the feed gas isfirst cooled and partially condensed and delivered to a separator toprovide a first residue vapor and a first liquid containing C₂ whichliquid also contains lighter hydrocarbons. A first part of the firstliquid containing C₂ from the separator may be directed into aheavy-ends fractionation column, wherein the liquid is separated into asecond residue containing lighter hydrocarbons and a second liquidproduct containing C₂. A second part of the first liquid from theseparator is cooled. The second residue is cooled and partiallycondensed and then combined with the cooled second part of the firstliquid providing, upon separation, a third residue and a third liquid. Afirst part of the third liquid is cooled and fed to the light-endsfractionation column. A second part of the third liquid is fed directlyto the heavy-ends fractionation column. A part of the first residuevapor with a cooled first part of the third liquid are counter-currentlycontacted and comingled in a light-ends fractionation column to therebyprovide fourth residue vapor and liquid which are separately discharged.Cooling the first part of the third liquid prior to its introductioninto the light-ends fractionation column aids in mass and heat transfer.This cooling thereby provides for greater liquefaction of a higherpercent of the C₂ and heavier hydrocarbon components while the methanecontained in the first part of the third liquid is vaporized. The fourthliquid recovered from the light-ends fractionation column is heated thenintroduced to the heavy-ends fractionation column as a feed.

A better understanding of the invention will be had with reference tothe following description and claims, taken in conjunction with theattached drawings.

DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic flow diagram illustrating a method of practicing apreferred embodiment of the invention.

FIG. 2 is a schematic flow diagram illustrating a variation in thepreferred embodiment of the present invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

The improved processes of the present disclosure include the steps ofcooling a gaseous hydrocarbon-containing feed stream to form a firstvapor stream and a first liquid stream. A first part of the first liquidstream is transferred to a heavy-ends fractionation column while thefirst vapor stream is transferred to the bottom of a light-endsfractionation column. The heavy-ends fractionation column overheadvapor, which consists mainly of methane, ethylene, and/or ethane, iscooled and partially condensed. The cooled heavy-ends fractionationcolumn overhead is combined with a cooled second part of the firstliquid stream. The resulting stream is fed to a separator and separatedinto a third residue vapor and a third liquid. A first part of the thirdliquid is cooled and fed to the upper portion of the light-endsfractionation column. The liquid flows downwardly within the light-endsfractionation column and contacts gaseous ethylene and/or ethane andheavier hydrocarbons that flow upwardly. The methane portion of theliquid stream is vaporized by absorbing heat from the gaseousethylene/ethane and heavier hydrocarbons which causes theethylene/ethane and heavier hydrocarbons to condense and exit at thebottom of the light-ends fractionation column. The gaseous methane andlighter components within the light-ends fractionation column areremoved from the overhead as a product of the process. The second partof the third liquid may be used to reflux the heavy-ends fractionationcolumn. The fourth liquid at the bottom of the light-ends fractionationcolumn is removed and used to cool other process streams; thethus-heated fourth liquid is fed to the upper portion of the heavy-endsfractionation column. The liquid at the bottom of the heavy-endsfractionation column is removed as a product of the process.

The improved process of this invention is illustrated in a firstembodiment in FIG. 1. The incoming gas stream 1 at a temperature of 120°F. and a pressure of 827 psia passes through heat exchanger 38, so thatthe temperature thereof is reduced to about −72° F. with attendantpartial condensation. Pressure is reduced as the gas flows through theheat exchangers resulting in a pressure of 812 psia at −72° F. at whichthe raw gas is delivered into a separator 44. Within separator 44 thecooled gas stream is separated into a first liquid stream (stream 4) anda first residue vapor, stream 3. Stream 3 is passed through a turboexpander 46. The shaft of turbo expander 46 is connected directly to theshaft of the booster compressor 32. From the turbo expander, the firstresidue gas having a temperature of about −163° F. at 200 psia passes byway of stream 5 into a light-ends fractionation column 52.

From separator 44 a first part of the first liquid containing C₂ isconducted into a heavy-ends fractionation column 56 by way of stream 4A.A second part of the first liquid containing C₂ from stream 4 ischanneled by way of stream 4B through heat exchanger 42 where itstemperature is decreased. The cooled liquid exits the heat exchanger andcombines with the cooled residue stream 14 to form stream 16.

The second residue from heavy-ends fractionation column 56, having atemperature of about −132° F., is fed by way of stream 14 through heatexchanger 42, combines with the remainder of the liquid containing C₂from stream 4B above, and by way of stream 16 into the reflux separator57. A first part of the third liquid from the reflux separator 57 isrouted by stream 23 through heat exchanger 42 where its temperature isreduced. This liquid stream is then passed as scream 23A into thelight-ends fractionation column 52. The liquid from stream 23A passesdownwardly through the light-ends fractionation column 52 and encountersthe rising first residue gas from stream 5 so that mass and latent heattransfer occur. The second part of the third liquid from the refluxseparator 57 is routed by stream 26 to the heavy-ends fractionationcolumn 56.

The light-ends fractionation column 52 functions as a combination heatand mass transfer device. The column has two feed streams; that is,streams 5 and 23A, and two product streams; that is, streams 10 and 9.The light-ends fractionation column 52 consists of at least one, andpreferably more, theoretical liquid-vapor equilibrium stages.

Vapor enters the light-ends fractionation column by way of stream 5 as abottom feed while the top feed is by way of stream 23A which is a liquidenriched by condensed methane. The methane and lighter constituents andun-recovered ethylene and ethane, exit as a dew point vapor as a fourthresidue (stream 9) from the top tray or separation stage of thelight-ends fractionation column 52.

The top feed through stream 23A into the light-ends fractionation column52 and particularly the methane content thereof serves as a reflux inthe column. In flowing from stage to stage within column 52, the liquidmethane is vaporized and in turn the liquid is progressively enriched inethylene and ethane condensed from the upflowing bottom feed vapor fromstream 5.

The fourth liquid stream from the light-ends fractionation column 52,stream 10, provides process cooling in exchanger 42 while it is itselfwarmed and then fed to the heavy-ends fractionation column 56 forfurther separation.

The fourth residue gas (stream 9) discharged from light-endsfractionation column 52 passes through exchangers 42 and 38 and exitsthe heat exchanger system as stream 19. The third residue gas vapor instream 18 exiting the reflux separator 57 also pass through exchangers42 and 38 and exit the heat exchanger system as stream 28. The warmedvapor from the light-ends fractionation column (stream 19) is compressedin compressor 48 to the same pressure as stream 28 and combined withstream 28 to form stream 30. The combined vapors of stream 30 arecompressed in the booster compressor 32. At this stage, the methane richoff-gas in stream 21 has a temperature of 103° F. and a pressure of 187psia. If it is desired to return the discharge gas to the same systemfrom which the raw gas was taken, such as for further transportation ofthe gas, the pressure will need to be raised back to that substantiallyequal to the Incoming pressure of 827 psia in stream 1.

The second liquid discharge, rich in C₂ content, from the lower end ofthe heavy-ends fractionation column 56 is passed by way of stream 15 andexchanger 38 to product discharge stream 22.

The result of a simulation of the process of FIG. 1 is set forth inTable 1A wherein the moles per hour of venous constituents of thestreams are set forth. The process achieves a recovery of about 97.37percent of the C₂ content of the feed gas in addition to substantiallycomplete recovery of the C₃ and heavier hydrocarbon components of thefeed gas stream into the less volatile fraction (product).

Table 1B relates the moles per hour of various constituents of thestream of the process of FIG. 1 when the process of FIG. 1 is applied toa feed gas stream that is enriched in ethane and heavier components.

FIG. 2 shows an alternate embodiment of the invention. The components ofthe process of FIG. 2 having the same basic structure and function ofthose of the system of FIG. 1 are given like numbers. The process is asdescribed with reference to FIG. 1, except that the booster compressor32 is placed on the feed gas (stream 1) and streams 9 and 18 arecombined prior to exchanger 42.

Table 2, shows the result of a simulation of the system of FIG. 2. Table2 provides the moles per hour of various constituents for the variousstreams of this embodiment of the process. The process achieves arecovery of about 91.64 percent of the ethylene and 96.77 percent of theethane content of the feed gas in addition to substantially completerecovery of the C₃ and heavier hydrocarbon components of the feed gasstream in to the less volatile fraction (product).

The process has been illustrated using various standard componentsemployed for the sequence of treating steps with it being understoodthat the process may be practiced utilizing different physicalapparatus. For instance, the turbo expander can, in many instances, beeliminated or replaced by a Joule-Thomson isenthalpic control valve. Thedifference is that where the expander is eliminated or where theJoule-Thomson valve is substituted for the turbo expander, normallygreater inlet and refrigeration compression duties are required.

A different arrangement has been shown in the alternate embodiment forcooling the second residue effluent and thus providing reflux to thelight-ends fractionation and heavy-ends fractionation columns.

Some of the processes in each instance may use multiple turbo expanders.The desirability of the use of multiple turbo expanders is predicatedprimarily upon the amount of hydrogen content of the inlet gas in stream1. It is understood that, according to the inlet gas content, onlysingle turbo expanders may be employed in practicing the process; or, insome instances as previously indicated, turbo expanders may beeliminated completely or substituted by one or more Joule-Thomsonisenthalpic expansion valves.

An important feature of the process is the employment of the light-endsfractionation column 52 which functions as a combination heat and masstransfer device. The use of the reflux in the top stage means that theliquid methane of the reflux is vaporized; and in turn the liquid isprogressively enriched in ethylene and ethane condensed from theupflowing bottom feed vapor to thereby recover a higher percent of theC₂ components.

While the invention has been described with a certain degree ofparticularity, it is manifest that many changes may be made in thedetails of construction and the arrangement of components withoutdeparting from the spirit and scope of this disclosure. It is understoodthat the invention is not limited to the embodiments set forth hereinfor purposes of exemplification, but is to be limited only by the scopeof the attached claim or claims, including the full range of equivalencyto which each element thereof is entitled.

TABLE 1A Stream Number Name 1 3 4 5 9 10 14 16 18 23 NITROGEN 99.1793.86 5.31 93.86 92.74 2.50 7.81 7.81 6.43 1.38 CARBON 8.64 6.19 2.456.19 1.89 5.83 1.95 1.95 0.42 1.53 DIOXIDE METHANE 7552.91 6526.791026.12 6526.79 6374.89 1115.68 2131.34 2131.34 1168.58 963.78 ETHANE486.41 272.65 213.76 272.65 9.22 299.03 39.18 39.18 3.57 35.60 PROPANE198.31 56.60 141.71 56.60 0.04 58.45 1.92 1.92 0.03 1.89 I-BUTANE 36.665.59 31.07 5.59 0.00 5.67 0.08 0.08 0.00 0.08 N-BUTANE 63.30 7.19 56.117.19 0.00 7.27 0.08 0.08 0.00 0.08 I-PENTANE 20.83 1.16 19.67 1.16 0.001.17 0.01 0.01 0.00 0.01 N-PENTANE 20.63 0.86 19.77 0.86 0.00 0.86 0.000.00 0.00 0.00 HEXANE 19.29 0.29 19.00 0.29 0.00 0.29 0.00 0.00 0.000.00 TOTAL 8525.10 6971.27 1553.83 6971.27 6478.78 1496.83 2,182.362,182.36 1179.02 1004.35 LBMOL/HR MASS FLOW 160249 119227 41022 119227105232 30726 35770 35770 19055 16732 LB/HR VOLUME FLOW 78 63 — — 59 — 20— 11 — MMSCFD MOL MOLE, 18.80 17.10 26.40 17.10 16.24 20.53 16.39 16.3916.16 16.66 WT DENSITY 2.83 5.92 26.30 1.51 1.32 26.94 2.06 4.01 2.3520.51 LB/FT³ TEMPERATURE 120 −72 −72 −163 −178 −165 −132 −153 −153 −153° F. PRESSURE PSIA 827.00 812.00 812.00 200.00 193.00 385.00 330.00328.00 328.00 353.00 Percent Percent Recovered Recovered to to LessStream Number Volatile Volatile Name 25 26 15 22 21 Fraction FractionNITROGEN 0.00 0.00 0.00 0.00 99.17 100.00% 0.00% CARBON DIOXIDE 0.000.00 6.33 6.33 2.31 26.71% 73.30% METHANE 0.00 0.00 10.46 10.46 7543.4699.87% 0.14% ETHANE 0.00 0.00 473.61 473.61 12.79 2.63% 97.37% PROPANE0.00 0.00 198.24 198.24 0.07 0.04% 99.96% I-BUTANE 0.00 0.00 36.66 36.660.00 0.00% 100.00% N-BUTANE 0.00 0.00 63.30 63.30 0.00 0.00% 100.00%I-PENTANE 0.00 0.00 20.83 20.83 0.00 0.00% 100.00% N-PENTANE 0.00 0.0020.63 20.63 0.00 0.00% 100.00% HEXANE 0.00 0.00 19.29 19.29 0.00 0.00%100.00% TOTAL LBMOL/HR 0.00 0.00 868.31 868.31 7657.80 MASS FLOW LB/HR 00 35978 35978 124286 VOLUME FLOW — — — — 70 MMSCFD MOL MOLE, WT 16.6616.66 41.44 41.44 16.23 DENSITY LB/FT³ 20.51 20.51 30.11 27.97 1.03TEMPERATURE ° F. −153 −153 71 100 167 PRESSURE PSIA 353.00 353.00 500.00495.00 413.41

TABLE 1B Stream Number Name 1 3 4 5 9 10 14 16 18 23 NITROGEN 345.88280.87 65.02 280.87 275.89 16.91 19.90 84.91 69.99 11.93 CARBON 327.77161.06 166.70 161.06 48.44 254.24 37.16 203.85 26.83 141.62 DIOXIDEMETHANE 24864.18 16379.96 8484.21 16379.96 17115.17 6530.39 8271.6616754.42 7672.43 7265.60 ETHANE 3696.03 1309.26 2386.76 1309.26 179.473053.40 131.47 2518.25 113.74 1923.61 PROPANE 2012.72 363.60 1649.12363.60 10.96 1673.25 11.09 1660.25 9.49 1320.61 I-BUTANE 385.41 40.55344.87 40.55 0.43 316.09 0.54 345.41 0.46 275.96 N-BUTANE 612.71 50.73561.98 50.73 0.35 500.03 0.49 562.47 0.41 449.65 I-PENTANE 151.53 7.05144.48 7.05 0.02 122.62 0.03 144.51 0.03 115.59 N-PENTANE 115.29 4.29111.00 4.29 0.01 93.09 0.01 111.02 0.01 88.80 HEXANE 98.82 1.67 97.151.67 0.00 79.39 0.00 97.15 0.00 77.72 HYDROGEN 0.00 0.00 0.00 0.00 0.000.00 0.00 0.00 0.00 0.00 SULFIDE CARBONYL 3.29 0.68 2.61 0.68 0.03 2.740.03 2.64 0.03 2.09 SULFIDE Total 32613.64 18599.74 14013.90 18599.7417630.77 12642.15 8472.40 22484.88 7893.41 11673.17 LBMOL/HR MASS FLOW705883 339451 369432 339451 290366 352036 139402 508812 130123 302951LB/HR VOLUME 297 169 — — 161 — 77 — 72 — FLOW MMSCFD Moie wt, 21.7418.25 26.36 18.25 16.47 27.85 16.45 22.63 16.48 25.95 DENSITY 4.20 6.8824.02 1.76 1.46 32.32 2.07 6.70 2.06 30.02 LB/FT3 TEMP ° F. 120 −40 −40−133 −149 −138 −129 −131 −131 −131 PRESSURE 978.00 966.35 966.35 242.00237.00 375.00 335.00 330.00 330.00 370.00 PSIA Percent Percent RecoveredRecovered to to Less Stream Number Volatile Volatile Name 25 26 15 22 21Fraction Fraction NITROGEN 2.98 2.98 0.00 0.00 345.88 100.00% 0.00%CARBON DIOXIDE 35.40 35.40 252.48 252.48 75.27 22.97% 77.03% METHANE1816.40 1816.40 75.13 75.13 24787.60 99.69% 0.30% ETHANE 480.90 480.903402.83 3402.83 293.21 7.93% 92.07% PROPANE 330.15 330.15 1992.301992.30 20.46 1.02% 98.99% I-BUTANE 68.99 68.99 384.53 384.53 0.89 0.23%99.77% N-BUTANE 112.41 112.41 611.95 611.95 0.76 0.12% 99.88% I-PENTANE28.90 28.90 151.49 151.49 0.04 0.03% 99.97% N-PENTANE 22.20 22.20 115.28115.28 0.02 0.02% 99.98% HEXANE 19.43 19.43 98.82 98.82 0.00 0.00%00.00% HYDROGEN SULFIDE 0.00 0.00 0.00 0.00 0.00 0.00% 00.00% CARBONYLSULFIDE 0.52 0.52 3.23 3.23 0.06 1.84% 98.16% Total LBMOL/HR 2918.292918.29 7088.04 7088.04 25524.18 MASS FLOW LB/HR 75738 75738 288372288372 420489 VOLUME — — — — 232 FLOW MMSCFD Mole wt, 25.95 25.95 40.6840.68 16.47 DENSITY 30.02 30.02 30.09 27.83 0.88 LB/FT3 TEMP ° F. −131−131 72 100 115 PRESSURE 370 370 500.00 490.00 317.14 PSIA

TABLE 2 Stream Number Name 1 3 4 5 9 10 14 16 18 23 HYDROGEN 1274.201203.16 71.03 1203.16 1200.28 3.85 29.12 75.29 73.92 0.96 NITROGEN197.10 165.03 32.07 165.03 162.81 5.39 17.96 38.80 34.30 3.16 CARBON13.01 10.54 247 10.54 10.36 0.52 1.53 3.13 2.65 0.34 MONOXIDE METHANE3194.56 1790.74 1403.81 1790.74 1992.70 641.30 1485.42 2397.90 1197.69843.29 ETHYLENE 672.81 127.55 545.26 127.55 29.42 356.01 39.41 393.8226.82 257.87 ETHANE 1402.52 155.95 1246.57 155.95 21.51 711.58 34.92845.19 23.80 577.13 PROPENE 195.47 5.89 189.58 5.89 0.24 92.39 0.64123.86 0.41 86.74 PROPANE 156.55 3.57 152.98 3.57 0.12 73.40 0.35 99.790.22 69.96 I-BUTANE 1.51 0.01 1.50 0.01 0.00 0.70 0.00 0.98 0.00 0.68N-BUTANE 81.73 0.45 81.28 0.45 0.00 37.57 0.02 52.86 0.01 37.13N-PENTANE 28.36 0.03 28.33 0.03 0.00 12.97 0.00 18.42 0.00 12.94 TOTAL7217.81 3462.92 3754.89 3462.92 3417.45 1935.67 1609.35 4050.03 1359.841890.19 LBMOL/HR MASS FLOW 142766 44774 97992 44774 40727 52131 2663490329 21995 48083 LB/HR VOLUME FLOW 66 32 — — 31 — 15 — 12 — MMSCFD MOLEWT 19.78 12.93 26.10 12.93 11.92 26.93 16.55 22.30 16.10 25.44 DENSITY2.13 2.82 28.62 0.71 0.63 33.86 1.07 3.84 1.03 31.33 LB/FT³ TEMPERATURE100 −89 −89 −171 −183 −175 −146 −152 −152 −152 ° F. PRESSURE PSIA 581.00726.00 726.00 148.60 145.00 213.00 185.00 181.00 181.00 213.00 PercentPercent Recovered Recovered to to Less Stream Number Volatile VolatileName 25 26 15 22 21 Fraction Fraction HYDROGEN 0.41 0.41 0.00 0.001274.20 100.00% 0.00% NITROGEN 1.34 1.34 0.00 0.00 197.11 100.00% 0.00%CARBON MONOXIDE 0.14 0.14 0.00 0.00 13.01 100.00% 0.00% METHANE 356.91356.90 4.21 4.21 3190.39 99.87% 0.13% ETHYLENE 109.14 109.14 616.58616.58 56.24 8.36% 91.64% ETHANE 244.26 244.27 1357.22 1357.22 45.323.23% 96.77% PROPENE 36.71 36.71 194.82 194.82 0.65 0.33% 99.67% PROPANE29.61 29.61 156.21 156.21 0.34 0.22% 99.78% I-BUTANE 0.29 0.29 1.51 1.510.00 0.00% 99.97% N-BUTANE 15.71 15.71 81.71 81.71 0.02 0.02% 99.98%N-PENTANE 5.48 5.48 28.36 28.36 0.00 0.00% 100.00% TOTAL LBMOL/HR 800.00800.00 2440.62 2440.62 4777.28 MASS FLOW LB/HR 20351 20351 80146 8014662622 VOLUME FLOW — — — — — MMSCFD MOLE WT 25.44 25.44 32.84 32.84DENSITY LB/FT³ 31.33 31.33 30.51 23.64 TEMPERATURE ° F. −152 −152 −7 74PRESSURE PSIA 213.00 213.00 585.00 580.00

1. A process for separation of a feed gas containing methane, C₂ and heavier hydrocarbon components into a volatile residue gas fraction and a relatively less volatile fraction containing said C₂ components and heavier hydrocarbon components, said process comprising: (a) cooling said feed gas in one or more heat exchangers and then separating the cooled feed gas in a separator into a first residue vapor and a first liquid which contains C₂ and other lighter and heavier hydrocarbons; and (b) delivering a first part of said first liquid containing C₂ to a heavy-ends fractionation column wherein said first liquid is separated into a second residue containing lighter hydrocarbons and a liquid product containing C₂; (c) cooling said second residue to partially condense it; (d) cooling a second part of said first liquid containing C₂ from (b) and combining the cooled second part of said first liquid with the partially condensed second residue stream from (c) resulting in the formation of a third liquid stream and a third residue vapor; (e) dividing said third liquid produced in (d) into first and second parts; (f) further cooling the first part of said third liquid; (g) directing the second part of the third liquid to said heavy-ends fractionation column; (h) intimately contacting at least part of said first residue vapor with the cooled first part of third liquid from (f) in at least one contacting stage and thereafter separating a fourth residue vapor and a fourth liquid containing C₂ from said at least one contacting stage; (i) supplying said fourth liquid to a heat exchanger for heating said fourth liquid, and thereafter supplying said fourth liquid into said heavy-ends fractionation column as a feed thereto; (j) recovering as product the combined heated third residue vapor and said fourth residue vapor; and (j) recovering as product said second liquid stream from said heavy-ends fractionation column.
 2. The process according to claim 1, wherein said intimately contacting of said at least part of said first residue vapor with said cooled first part of said third liquid is carried out in a light-ends fractionation column that includes fractionation means for vapor/liquid counter-current contact; said cooled first part of said third liquid is introduced into said light end fractionation column above said fractionation means, whereby said cooled first part of said third liquid passes downwardly through said light end fractionation means; and supplying at least part of said first residue vapor to said light-ends fractionation column below said fractionation means, whereby said first residue vapor rises through said fractionation means in counter-current contact with said cooled first part of said third liquid.
 3. The process according to claim 2, wherein said fractionation means in said light-ends fractionation column provides the equivalent of at least one theoretical liquid-vapor equilibrium stage arranged to contact at least part of said first residue vapor with said cooled first part of said third liquid stream.
 4. The process according to claim 1, further comprising cooling said first part of said third liquid prior to delivery of said first part of said third liquid to said light-ends fractionation column.
 5. The process according to claim 1, further comprising cooling said second part of said first liquid prior to combination of said second part of said first liquid with the partially condensed second residue stream.
 6. A process for separating a feed gas containing at least methane, C₂ components and heavier components, said process comprising: (a) separating said feed gas in a first separation means to produce a first residue vapor and a first liquid containing C₂ and lighter hydrocarbons; (b) introducing at least a portion of a first part of said first liquid containing C₂ to a heavy-ends fractionation column, said separating said first part of said first liquid containing C₂ in said heavy-ends fractionation column into a second residue vapor containing lighter hydrocarbons and a second liquid containing C₂ product; (c) introducing at least a part of said first residue vapor into a light-ends fractionation column, said light-ends fractionation column having at least one contacting stage, removing a fourth vapor from said light-ends fractionation column, and removing a fourth liquid from said light-ends fractionation column and delivering said fourth liquid to said heavy-ends fractionation column; (d) supplying at least part of a second part of said first liquid containing C₂ to a reflux separator positioned between said first separation means and said heavy ends fractionation column, removing a third liquid from said reflux separator, and removing a third residue vapor from said reflux separator; (e) delivering a first part of said third liquid to a heat exchanger to cool said first part of said third liquid, and delivering at least part of the cooled first part of said third liquid from said heat exchanger to said light-ends fractionation column, wherein said at least part of said first residue vapor and said at least part of the cooled first part of the third liquid commingle in said at least one contacting stage, and (f) delivering a second part of said third liquid to said heavy-ends fractionation column means.
 7. A process according to claim 6, wherein said light-ends fractionation column comprises fractionation means for counter-current vapor-liquid contact, and wherein said first residue vapor is introduced into said light-ends fractionation column at a point below said fractionation means.
 8. A process according to claim 7, wherein said at least part of said first residue is introduced into said light-ends fractionation column at a point below said fractionation means, and said at least part of the cooled first part of said third liquid from said heat exchanger is introduced into said light-ends fractionation column at a point above said fractionation means.
 9. A process according to claim 6, further comprising combining at least a portion of said second residue vapor from said heavy-ends fractionation column with said at least part of the cooled first part of said third liquid before introduction into said light-ends fractionation column means.
 10. A process according to claim 6, further comprising combining said third residue vapor from said reflux separator with said fourth vapor from said light-ends fractionation column.
 11. A process according to claim 6, further comprising combining said at least a portion of a first part of said first liquid containing C₂ and said fourth liquid from said light-ends fractionation column before being introduced into said heavy-ends fractionation column means.
 12. A process for separating a hydrocarbon feed gas into a lighter fraction containing methane and a heavier fraction containing C₂ hydrocarbons, said process comprising: introducing a hydrocarbon feed gas containing methane, C₂ hydrocarbons, and heavier hydrocarbons into a separator, and removing from said separator a first residue vapor, and a first liquid, introducing at least a part of said first residue vapor into a light-ends fractionation column, and removing from said light-ends fractionation column comprising a fourth residue vapor containing methane, and a fourth liquid, introducing at least a portion of said first liquid into a heavy-ends fractionation column, and removing from said heavy-ends fractionation column a second residue vapor, and a second liquid containing C₂ hydrocarbons, and introducing at least a portion of a second part of said first liquid into a reflux separator, and removing from said reflux separator a third residue vapor, and a third liquid.
 13. A process according to claim 12, further delivering at least a portion of said fourth liquid from said light-ends fractionation column to said heavy-ends fractionation column.
 14. A process according to claim 12, further comprising delivering at least a portion of said second residue vapor from said heavy-ends fractionation column to said light-ends fractionation column.
 15. A process according to claim 13, further comprising delivering at least a portion of said second residue vapor from said heavy-ends fractionation column to said light-ends fractionation column.
 16. A process according to claim 12, further comprising delivering at least a portion of a first part of said third liquid to said light-ends fractionation column.
 17. A process according to claim 15, further comprising delivering at least a portion of a first part of said third liquid to said light-ends fractionation column.
 18. A process according to claim 12, further comprising delivering at least a portion of a second part of said third liquid to a said heavy-ends fractionation column.
 19. A process according to claim 17, further comprising delivering at least a portion of a second part of said third liquid to said heavy-ends fractionation column.
 20. A process according to claim 12, further comprising delivering at least a portion of said second residue vapor from said heavy-ends fractionation column to said reflux separator.
 21. A process according to claim 19, further comprising delivering at least a portion of said second residue vapor from said heavy-ends fractionation column to said reflux separator.
 22. A process according to claim 12, further comprising combining said third residue vapor and said fourth residue vapor.
 23. A process according to claim 12, further comprising expanding said first residue vapor in a turbo expander prior to introducing said first residue vapor into said light-ends fractionation column.
 24. A process according to claim 16, further comprising cooling said at least a portion of said first part of said third liquid in a heat exchanger prior to being introduced into said light-ends fractionation column.
 25. A process according to claim 17, further comprising cooling said at least a portion of said first part of said third liquid in a heat exchanger prior to being introduced into said light-ends fractionation column. 